Surprise! I'm doing Celestia and Luna too! Luna might take a few days, but she'll be along.
I know that the normal portrayal of young Celestia has a solid color pink mane, but I really wanted to try something else. My logic is mainly that Luna, who's mane is basically one color, just with stars and a hazy outline, has a solid color mane in the young/de-powered version. Twilight, who's mane has stripes, is canonically shown with basically the same pattern when she grows into an adult alicorn. Therefore, Celestia, who has a multicolor striped mane in the show, would have had a multicolor striped mane when she was young. Plus, I think it looks more interesting this way.
I also know that there is some contention over weather or not Celestia and Luna were born alicorns, or ascended. And if the later, what tribe they were before hand. I chose to have them both born as unicorns, as the whole "raising the sun and moon" thing is traditionally a unicorn task. They probably would have ascended by raising the sun and moon by themselves, without the help of a team.